This invention relates the regulation of the fiber quantities introduced into a fiber tuft feeding apparatus and concerns, in particular to a pressure-responsive electronic switch that includes an axially adjustable electronic proximity switch, a diaphragm spaced from the proximity switch and positioned in an orientation perpendicular to the axis thereof and a metal plate supporting the diaphragm in a face-to-face relationship therewith. There is further provided a compression spring arranged coaxially about the proximity switch and biasing the metal plate.
In a known electronic pressure-responsive switch of the above-outlined type the compression spring yields as the external pressure which is to be sensed and to which the diaphragm is exposed, increases so that upon reaching a predetermined setting pressure, the metal plate arrives in the switching zone of the electronic proximity switch. Upon this occurrence, a thyristor contained in the proximity switch fires and thus causes a voltage to appear at the output of the pressure-responsive switch. If the external pressure to be sensed drops below a set switching pressure, the thyristor blocks, resulting in a disappearance of the voltage from the output of the pressure-responsive switch.
An electronic pressure-responsive switch of the above-outlined type may constitute a measuring member of a regulating circuit for a fiber tuft feeding apparatus serving a carding machine. Such a regulating circuit comprises a regulator and further, a tuft feeding roll of the feeding apparatus constitutes, a setting member. Such a system, including the above-outlined pressure-responsive switch, is disclosed in U.S. Pat. No. 4,161,052, issued July 17th, 1979.
With a pressure-responsive switch disclosed in the above patent, only a two-point regulation can be obtained. Thus, upon exceeding or falling below a predetermined pressure, the feeding roll is deenergized or energized. Since the conventional electronic proximity switch emits a digital electric signal, the feeding roll cannot be regulated continuously and in a stepless manner.